This invention relates to an image forming system having a personal computer for a client connected on a local network and a plurality of color digital copying machines having a printing function connected via a controller, for example.
In recent years, an image forming system having a personal computer (client PC, terminal) for a client connected on a local network (LAN, communication line) and a plurality of color digital copying machines (printing devices) having a printing function connected via a controller is proposed.
In the image forming system, a printing process is effected by the digital copying machine based on a printing job from the client PC.
In the above image forming system, private printing can be effected in order to protect the security of the printing job.
The private printing is effected as follows.
First, private printing is instructed and a password is input when printing is instructed by the client PC.
Further, printing jobs for the private printing are previously stored in the printing device and a list of printing jobs for the private printing stored is displayed based on the instruction of the private printing from a control panel. According to this display, a printing job which is desired to be printed is selected and the same password as the password input by the client PC is input. If the passwords coincide, the digital copying machine performs the printing of the printing job.
By using the above method, the security when printing of high security level such as a confidential document, for example, is performed is attained (refer to Pat. Appln. KOKAI Publication Heisei No. 11-31061).
Further, in the above image forming system, when a large number of copies are printed, a system in which loads of the printing job are distributed (tandem printed) to two or more printing devices to enhance the processing speed is proposed (refer to Pat. Appln. KOKAI Publication Heisei No. 11-282645).
If the client PC specifies the distributed printing process (tandem printing) in the two or more printing devices for such a large number of copies, the instruction specified by the client PC cannot be changed on the printing device side.
That is, the tandem printing is to distribute a large amount of printings to a plurality of printing devices and process the same and time can be reduced by instantly starting when printing data is supplied to each printing device.
Therefore, a concept of switching to single printing for collectively printing them by one printing device after the client PC specifies the tandem printing is not present.
Further, if an attempt is made to effect the tandem printing when the private printing is effected, printing is effected by different printing devices installed in different places and the inherent security of the private printing does not function, and therefore, the tandem printing is set so as not to be effected when the private printing is effected.
However, in a state wherein a plurality of printing devices which effect the tandem printing are set close to each other and the printing operations thereof can be simultaneously monitored, the tandem printing can be effected at the time of private printing without losing the security function.
Since it is required to effect a subject identifying process on the printing device side when the tandem printing is effected at the time of private printing, it is desired to develop a system in which the tandem printing and single printing can be switched at the above processing time.